Drier for gas-cooling systems



' March 20, 1945. c c, T RR TT 2,372,135

DRIER FOR GAS-COOLING SYSTEMS Filed Oct. 30, 1942 O 0 O O 0 O 0 OWITNESSES:

INVENTOR ATTORNEY.

Patented Mar. 20, 1945 UNITED STATES PATENT OFFICE DRIER FOR GAS-COOLINGSYSTEMS Charles C. Sterrett, Wilkinsburg, Pa., assignor to WestinghouseElectric & Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application October 30, 1942, Serial No. 463,987

4 Claims.

ing enclosed in a substantially gas-tight housing,

with means for recirculating the gas contained within the housing, andcausing the recirculated gas to pass over cooling tubes or coils inwhich a cooling liquid is circulated. The recirculated gas may behydrogen, or carbon dioxide, or air, or any other gaseous medium. Thegas, when first introduced into the generator-housing, may have acertain moisture-content, or humidity, or degree of saturation as tomoisture-content, and whether it originally had this moisture-content ornot, the ventilating-system is subject to leakage, not only at theshaft-seals, but also at other points, so that moisture-laden air is aptto infiltrate into the closed gaseous system within the housing duringthe operation of the machine. Since the cooling coils reduce thetemperature of this moisture-laden gas in the machine, a point willobviously be reached at which the moisturecontent at the reducedtemperature will exceed the saturation-point of the gas at saidtemperature, causing precipitation or condensation of moisture,resulting in the formation of water which may either fiow onto thewindings, or be carried onto the windings by the high velocity of themoving gas, resulting ultimately in damage to the electrical insulationwhich protects the winding.

Heretofore, it has been customary to equip such machines with agas-drier, and a common form of such a drier has been a chamber filledwith activated alumina, which was connected in an auxiliaryrecirculating path, usually connected across the generator-fan, so thatgas was normally circulated through the drier whenever the machine wasrunning. This type of drier had the disadvantage, however, not only ofbeing somewhat costly, but also requiring quite considerablesupervision, and rather frequent periods of shut-down, during which thedrier had to be disconnected from service, and put through a specialheating-process for re-activating the alumina, requiring hours of timeand attention on the part of the station-attendant.

The principal object of my present invention is to provide a gas-drierfor the above-mentioned service, which is continuous in its operation,inexpensive in its first installation-cost and in its maintenance, andoperable without any super vision, either without any supervision atall, or without any supervision over and above that which prudencedictates should be given to the gas-cooled generator, regardless thenature of the drier.

With the foregoing and other objects in view, my invention consists inthe apparatus, parts, combinations, systems and methods hereinafterdescribed and claimed, and illustrated in the accompanying drawing, thesingle figure of which is a somewhat diagrammatic longitudinal sectionalview illustrating the principles, of embodimentof my invention in apreferred form of embodiment.

I have'illustrated my invention in connection with a hydrogen-cooledturbine-generator, only the collector-end half of which is illustrated,it being understood that the turbine-end is, or may be, essentiallysimilar, so far as the essential features of my present invention areconcerned. The generator is provided with a stator 2 and a rotor 3,having insulated electrical windings 4 and 5, respectively, which areliable to damage if long subjected to an excessive amount of moisture.The entire generator is enclosed in a sub stantially gas-tight housing6, which is filled with a gaseous medium 1 which may be hydrogen, carbondioxide, air, or other gaseous medium, although the particular machinewhich was shown was intended to be utilized with hydrogen as the coolinggas, and with carbon-dioxide as the scavenging gas for displacing theair before admitting the hydrogen. The rotor 3 is provided with a shaft8 which is journaled in bearings 9 which are subject to small continualinfiltrations of moisture-laden air from outside of the machine.

The hydrogen 1, which fills the chamber provided by the housing 6, isrecirculated by means of a fan I l which is carried by the shaft 8 ateach end of the rotor 3, and a system of baiiles [2, I3, I and the likeare provided for directing the hydrogen into and over the stator 2 androtor 3, and the windings 4 and 5 carried thereby, in any known ordesired manner, for the purpose of cooling the same. After passingthrough or over the electrical parts of the machine, the hydrogen isthen caused to flow through or over a cooler l6, and hence back to thelow-pressure side I! of the fan H, some of the gas-flow paths beingindicated by the arrows.

The cooler I 6 is the main cooler of the machine,

and is of considerable size, usually two coolers being provided, one ateach end of the machine, or else a plurality of coolers are provided,extending longitudinally of the machine. These coolers Iii consist ofpipes or coils I8, through which water is circulated, the water beingadmitted through an intake-pipe 20, and discharged through anoutlet-pipe 2 I.

As previously explained, and as is well known, unless themoisture-content of the recirculated gas is reduced by artificial means,the gas is likely to be chilled below its dew point, inv passing throughthe cooler l6, so that water has to be collected in a tray 22 underneaththe cooler,

and it sometimes may overflow into other arts of the machine, besidesbeing mechanically entrained and carried along, in the form of liquiddroplets, by reason of the high velocity of movement of therecirculating gas which is utilized to cool the machine.

My invention relates to a special means for drying the recirculatedcooling-gas I, so that it will not give up any substantial amount ofwater, or any water at all, in passing through the main cooler IE, or inpassing over, or in heatexchanging relation to, the cooling-coils l8,which constitute the cooler-proper. My invention is based upon thediscovery that the temperaturegradient which necessarily exists betweenthe water in the cooling-coils l8 and the recirculated gas which passesthereover is suflicient to provide a practically operating meanswherebythe gas can be prevented from reaching its saturationpoint, or dewpoint, in passing over or through thisvmain cooler I6-I8. Inpracticalmachines,

lower temperature than is produced at any other.

point in the entire gas-circulating system.

In the illustrated case, the gas-1eaving the auxiliary cooler 38 is 6cooler than the gas leaving the main cooler 13, which is another way ofsaying that, when the gas leaves the auxiliary cooler 33, through thepipe 36, and mixes with the lowpressure gas in the space ll of the, mainmachine, it mixes with a relatively large quantity of gas which is 6warmer than itself. If the gas is at its saturation-point at its coldesttemperature, where any excess water-vapor, over and above the amountwhich can be carried in vapor form, has been precipitated or condensedout of Y the gas, in the auxiliary cooler 33, a 6 rise ingas-temperature is enough to produce a relative humidity of about 80% inthe gas, which is well below the saturation-point, giving a sufficientmargin of safety to assure thatobjectionable this temperature-gradientis of the order of 7 F.

In accordance with my invention, I draw oiT a small percentage of therecirculated gas, as by means of a pipe 30, which is connected on thehigh-pressure side 3! of the fan H, and I supply this relatively smallpercentage of the recirculated gas, through a gas-flow control-orifice32, to an auxiliary cooler 33, which contains water-circulatingcooling-coils 34, and which has a'watersump or reservoir 35 in whichwater or other condensate 'may be collected. This auxiliary cooler 33 isin an auxiliary recirculated-gas path which is completed by means of anoutlet gaspipe 36, extending from above the water-sump 35 in the cooler33, to a point on the low-pressure side i! of the fan H within thegenerator-housing 6. The cooling-coils 34 in the auxiliary cooler 33 arecooled with water which is obtained from the same water-supply systemiii-2| as the main coolers l6, as by means of the pipe-connections 4Gand 4|, respectively, the rate of water-flow in the auxiliary coolerbeing controlled by means of a suitable valve 42.

In accordance with my invention, I cause the small amount of gas whichcirculates in the auxiliary circulating path 30-33-33 to flow at such arestricted velocity, as controlled by the gas-flow control-orifice 32,that only a small temperature-gradient, such as a gradient of, say, 1F., exists between the gas as it leaves the auxiliary cooler 33 and theinlet-water which enters the water-pipes or coils 34 of theauxiliarycooler. Since the auxiliary cooler is cooled by the samewater-supply which is utilized for the main coolers Hi, the auxiliarycooler is at least as cool as the main cooler, and since thetemperature-- condensation of water-vapor is not obtained in the mainportion of the chamber enclosed by the generator-housing 6. This processneed not be carried on at a rapid rate, but by continuing slowly andconstantly, it holds down the moisture-content of the gas in thegenerator-chamber, so that its humidity, as it leaves the main coolerI6, is of theorder of 80%, or other value which is considerably lowerthan the saturationpoint.

Since only a relatively small quantity of gas is cooled in the auxiliarycooler 33, this cooler may be relatively small in size, so that its costand space-requirements are insifinigcant, as compared with those of themain cooler it.

The condensate-receiving sump or reservoir 35 of the auxiliary cooler 33is provided with a suitable drain-valve 53, which may be of either anautomatic type or a manual type. So far, I have preferred to utilize amanually operated drainvalve 50, which is opened once a day, to removethe water which has been condensed during the day, and to serve as avery valuable check in regard to the amount of leakage into thesupposedly gas-tight housing 6, because any increase in this leakagewill immediately show up in an increased amount of water collected forthat day.

From the foregoing description, it will be understood that I haveprovided a thoroughly reliable means'for drying the recirculated gas inan electrical energy-translating device having insulated windings, or,in fact, in any other chamber utilizing a recirculated, conditioned gas.By the simple expedient of reducing the temperature of the gas to thelowest temperature which it will have anywhere in the system, andcausing this lowest temperature to occur at a selected point locatedessentially out Of the main portion of the chamber, where the condensedwater or condensate from any other vapor will be harmless, I haveprovided a simple, reliable, and continuously operative means, wherebyit is assured that the gas, at every other point in the system, willhave a humidity which is safely below the saturation-point. By theexpedient of utilizing the same cooling-fluid to cool both of thecoolers, coupled with the expedient of causing the gas to flow moreslowly past the auxiliary cooler, I have provided a means forautomatically insuring that the temperature-gradient between the gas andthe cooling-fluid for the coolers is lower, in the auxiliary cooler,than in the main cooler, thus insuring a lower temperature for the gasas it leaves the auxiliary cooler. By withdrawing only a relativelysmall proportion of the recirculated gas, and passing it, in a slow,steady stream, past thonuxiliary cooler, and keeping up'ith'is processcontinuously, I am enabledlto dry or condition all or the gas intheentire gas-system or enclolow the moisture-condensing point, everywhereexcept at the auxiliary cooler where the condensate is readily andharmlessly collected, and I accomplish this with an auxiliary coolerwhich is so small that its cost is relatively negligible, and with agas-velocity in the auxiliary cooler which is so low that the condensedwater is not borne back into the main portion of the chamber by thegas-flow.

While I have described my invention, and illustrated it in a singleillustrative form of embodiment, with a somewhat simplified anddiagrammatic showing, it will be obvious that many minor changes inarrangement and detail may be made, within the skill of those skilled inthe art, without departing from the essential spirit of my invention. Idesire, therefore, that the appended claims shall be accorded thebroadest construction consistent with their language.

I claim as my invention:

1. The combination, with a chamber in which a. conditioned gaseousmedium is to be recirculated; of means for maintaining a mainrecirculating-gas path for the main portion of the recirculated gas ofsaid chamber; a large-sized main gas-cooler located in heat-exchangingrelation with respect to a portion of said main recirculating-gas path;means for maintaining an auxiliary recirculating-gas path for only asmall portion of the recirculated gas of said chamber; a small-sizedauxiliary gas-cooler located in heat exchanging relation with respect toa portion of said auxiliary recirculating-gas path at a pointessentially out of said main recirculating-gas path; a substantiallycommon cooling-medium for cooling both of said coolers, so that theauxiliary cooler is at least as cool as the main cooler; and means forcausin the velocity of the gaseous medium which passes inheat-exchanging relation to the auxiliary cooler to be lower than thatwhich passes in heat-exchanging relation to the main cooler, wherebythere is a lower temperature-gradient between the cooled gaseous mediumand the cooling medium in the region of the auxiliary cooler than in theregion of the main cooler.

2. The combination, with a chamber in which a conditioned gaseous mediumis to be recircue lated; of main-duct means for providing a mainrecirculating-gas path for the main portion oi" the recirculated gas ofsaid chamber; fan-means for maintaining gas-flow in said main-duct path;a large-sized main gas-cooler located in heatexchanging relation withrespect to a portion of said main recirculating-gas path; auxiliary-ductmeans for withdrawing a relatively small portion of the recirculatedgaseous medium from one point in said main recirculating-gas path andreturning it at another point at a lower gas-pressure in said mainrecirculating-gas path, thereby providing an auxiliary recirculating-gaspath; a small-sized auxiliary gas-cooler located in heatexchangingrelation with respect to a portion of said auxiliary recirculating-gaspath at a point essentially out of said main recirculating-gas path; asubstantially common cooling medium for cooling both of said coolers, sothat the auxiliary cooler is at least as cool as the main cooler; andmeans for causing the velocity of the gaseous medium which passes inheat-exchanging relation to the auxiliary cooler to'bc lower than thatwhich passes in heat-exchanging relation to the main cooler, whereby therecirculated gaseous medium reaches its lowest temperature, of anywherein the entire system, in the vicinity of said auxiliary cooler, saidlowest temperature being above the freezing-point of the principalcondensed vapor obtained from said recirculating gaseous me dium; acondensate-receiving receptacle in said auxiliary recirculating-gas pathfor receiving the condensate produced by said auxiliary cooler; anddraining-means for said receptacle.

3. A cooled electrical energy-translating device having insulatedelectric windings susceptible to damage upon long-continued exposure tomoisture, an approximately gas-ti ht housing for said energy-translatingdevice, a filling of a gaseous medium in said housing under conditionsin which said gaseous medium may carry water-vapor in suspensiontherein, main-duct means for providing a main recirculating-gas path forthe main portion of the gaseous medium within said housing, fan-meanswithin said housing for mantaining a continuous recirculation of saidgaseous medium around said main recirculating-gas path while saidelectrical energy-translating device is in operation, a main gas-coolerlocated in heatexchanging relation With'respect to a portion of saidmain recirculating-gas path within said housing in a place wheremoisture-condensation from said recirculated gaseous medium is undesirable, auxiliary-duct means for withdrawing a relatively small portionof the recirculated gaseous medium from said main recirculating-gas pathand returning it; to said main recirculatinggas path, thereby providingan auxiliary recirculating-gas path, and a gas-drying means in saidauxiliary recirculating-gas path at a point essentially out of the mainportion of said housing, said gas-drying means comprising a relativelysmallsized auxiliary gas-cooler located in heat-exchanging relation withrespect to a portion of said auxiliary recirculating-gas path, asubstantially common cooling-medium for cooling both of said coolers, sothat the auxiliary cooler is at least as cool as the main cooler, andmeans for causing the velocity of the gaseous medium which passes inheat-exchanging relation to the auxiliary cooler to be lower than thatwhich passes in heat-exchanging relation to the main cooler, wherebythere is a lower temperature-gradient between the cooled gaseous mediumand the cooling medium in the region of the auxiliary cooler than in theregion of the main cooler.

4. A cooled electrical energy-translating device having insulatedelectric windings susceptible to damage upon long-continued exposure tomoisture, an approximately gas-tight housing for said energy-translatingdevice, a filling of a gaseous medium in said housing under conditionsin which said gaseous medium may carry water-vapor in suspensiontherein, main-duct means for providing a main recirculating-gas path forthe main portion of the gaseous medium within said housing, fan-meanswithin said housing for maintaing a continuous recirculation of saidgaseous medium around said main recirculating-gas path while saidelectrical energy-translating device is in operation, a main gas-coolerlocated in heatexchanging relation with respect to a portion of saidmain recirculating-gas path within said housing in a place wheremoisture-condensation from said recirculated gaseous medium isundesirable, auxiliary-duct means for withdrawing a relatively smallportion of the recirculated gaseous medium from a point on thehigh-pressure side of the fan-means in said main recirculating-gas pathand returning it at a point on the low-pressure side of the fan-means insaid main recirculating-gas path, thereby providing an auxiliaryrecirculating-gas path, a relatively small-sized auxiliary gas-coolerlocated in heatexchanging relation with respect to a portion of saidauxiliary recirculating-gas path at a point essentially out of the mainportion of said housing, a substantially common cooling-medium forcooling both of said coolers, So that the auxiliary cooler is at leastas cool as the main cooler, means for causing the velocity of thegaseous medium which passes in heat-exchanging relation to the auxiliarycooler to be lower than that which passes in heat-exchanging relation tothe main cooler, whereby the recirculated gaseous medium reaches itslowest temperature, of anywhere in the entire system, in the vicinity ofsaid auxiliary cooler, said lowest temperature being above thefreezing-point of the condensed water obtained from said recirculatinggaseous medium, a condensate-receiving receptacle in a recirculatinggaspath for receiving the condensate produced by said auxiliary cooler, anddraining-means for said receptacle. l I

CHARLES C. STERRETI.

